1. FIELD OF THE INVENTION
The present invention relates to a hydrostatic continuously variable transmission comprising a swashplate type hydraulic pump having a pump cylinder which is integrally and coaxially coupled with a motor cylinder of a swashplate type hydraulic motor, an annular higher pressure oil passage communicating with motor ports located in an expansion stroke region of the hydraulic motor, an annular lower pressure oil passage communicating with motor ports located in a shrinkage stroke region of the hydraulic motor, both the higher and lower pressure oil passages being concentrically formed between the pump and motor cylinders, a large number of radially arranged distributor valves reciprocally movable between radially inner and outer positions to put a large number of pump ports in the hydraulic pump into alternate communication with the higher and lower pressure oil passages, and an eccentric ring circumscribed about the distributor valves and connected to an input member of the hydraulic pump for movement between a clutch OFF position and a clutch ON position, so that the distributor valves are controlled to put the pump ports located in a discharge stroke region of the hydraulic pump into communication with the higher pressure oil passage and the pump ports located in an intake stroke region into communication with the lower pressure oil passage in a first eccentric position of the eccentric ring and to bring the hydraulic pump into a short-circuited state in a second eccentric position of the eccentric ring.
2. DESCRIPTION OF THE PRIOR ART
The present applicant has already proposed such hydrostatic continuously variable transmission, as disclosed in Japanese patent Application Laid-open No. 224769/87.
In the hydrostatic continuously variable transmission already proposed, an external operating member is connected to the eccentric ring through a cam mechanism, so that the operating member is manually operated to control the position of the eccentric ring. Therefore, the structure is complicated and the operation is troublesome.